The physics of AGN feedback in galaxy clusters

Speaker

Talk Date

Talk Series

Christopher Reynolds, University of Maryland

26 February 2015

Institute of Astronomy Colloquia

Abstract

Cooling-core galaxy clusters give us a unique opportunity to
study an important aspect of galaxy formation — we believe that energy
injection by the active galactic nucleus (AGN) in the central galaxy
prevents catastrophic cooling of the intracluster medium (ICM), essentially truncating growth of these massive galaxies. After briefly reviewing these arguments, I shall discuss the theoretical questions that arise when one attempts to understand the detailed physics of AGN heating and regulation. At every level of description, the ICM/AGN system proves to be rich in physics. If the ICM is considered within simple hydrodynamics, questions arise as to how the AGN energy is thermalized and whether/how it drives bulk ICM turbulence. Adding magnetic fields and transport processes to our description (i.e. a Braginskii-MHD picture), the ICM atmosphere becomes
plagued by new convective instabilities that can strongly affect the ICM
thermodynamics. Finally, I will argue that plasma-scale kinetic physics may
have some important consequences for the ICM thermodynamics. Preliminary
results from particle-in-cell plasma simulations relevant to the ICM will be
presented.